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| Welding cast iron for vertical tension rods ? https://www.rypn.org/forums/viewtopic.php?f=1&t=25168 |
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| Author: | Matt Bumgarner [ Sat Apr 19, 2008 3:42 pm ] |
| Post subject: | Welding cast iron for vertical tension rods ? |
On our narrow gauge Lawndale boxcar, we are to the point where we are ready to place the new side sills; however, to do this, we need to cut the cast iron vertical tension rods. Since we do not plan on replacing or reworking the roof (which is in excellent condition and the reason the car survived), our plan was/is to cut the rods in two, drop out the lower corroded and laminated halves, install the new side sill, and run new STEEL rods up to the surviving tension rod half. At that point, we were going to weld the new rod to the old, but someone has brought up the question of the integrity of the weld between the old cast iron material and the new steel material. Any thoughts on this? Alternatively, we could use a tap and die set to join the halves together as well. Any way we go, the new connecting joints of the rods will be inside the walls and hidden from view. Any thoughts, comments, and suggestions on this topic are greatly appreciated. Matt Bumgarner Alexander Chapter NRHS |
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| Author: | Dave [ Sat Apr 19, 2008 6:16 pm ] |
| Post subject: | Re: Welding cast iron for vertical tension rods ? |
Hi Matt: I am a bit leery of welding old cast iron of indeterminate quality in situ. It is difficult enough to do a good reliable job of it under controlled conditions on a bench, with a rod and procedure adapted to a known quality of material. Is it possible to split off the nuts from the bottom of the rods, run a die up to chase the threads, and replace the nuts, or are the rods themselves too far gone? I'd recommend a mechanical connection to good material if you must replace the bottoms of the rods. Welded old cast iron in tension makes me nervous. Dave |
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| Author: | SouPac [ Sat Apr 19, 2008 9:00 pm ] |
| Post subject: | Re: Welding cast iron for vertical tension rods ? |
Are we sure we are dealing with cast iron or could it be wrought iron? It seems to me that cast iron is unlikely for a tension member in a wooden car due to it's brittle nature and low tensile strength. That being said, if it is wrought iron, it does not make welding much easier as slag inclusions and grain structure make for potential failure of the weld. I would agree with using a mechanical means of joining if preservation of the rod is impossible. This should be done with caution as the root diameter of the threads should not be below the required tensile strenth of the part. I hope this is of some help. Best, Stathi |
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| Author: | Matt Bumgarner [ Sat Apr 19, 2008 9:04 pm ] |
| Post subject: | Re: Welding cast iron for vertical tension rods ? |
Hi Dave, Unfortunately, the bottom of the rods are just too far gone. They are probably 30-50% smaller in diameter at the bottom than the upper half. In addition to considering the weld, we are considering threading good section of the rods and connecting them to a tapped junction section of the newer material. The upper half of the rods are in great shape, but like you, several of us have some reservations about welding the older material to a newer and fairly dissimilar rod. Thanks for your input on this and the previous questions as well! Matt |
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| Author: | Matt Bumgarner [ Sat Apr 19, 2008 9:07 pm ] |
| Post subject: | Re: Welding cast iron for vertical tension rods ? |
Yes, it could be wrought iron, but the way it has corroded and laminated sure reminds me of some older artifacts that I have seen which are definitely cast iron. It is extremely brittle as well, but that could also be due to the corroded nature of the item. Thanks for the input! Matt |
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| Author: | Randy Hees [ Sat Apr 19, 2008 9:24 pm ] |
| Post subject: | Re: Welding cast iron for vertical tension rods ? |
I would strongly suggest you are dealing with wrought iron, not cast iron… Cast iron would be used in compression, rarely (never?) in tension. I would say the same about wood, but several years ago encountered a covered bridge built to the “Smith Patent” which used wood in place of the more typical iron tension rods. On to more practical advice, when rebuilding our1882 narrow gauge combine we ran into a similar problem. We had to replace a section of side sill, didn’t want to disturb the roof, so ended up cutting the tension rods, threading the remaining end, then using modern threaded couplings and new steel rod to reassemble the car. Our tension rods were wrought iron… It was slow work to thread the end of the old rod, being in a tight space between posts and the inside sheeting of the car… |
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| Author: | david griner [ Sat Apr 19, 2008 11:19 pm ] |
| Post subject: | Re: Welding cast iron for vertical tension rods ? |
The significant factor in this case is knowing exactly what is being welded. The old piece can be evaluated by a "spark test", done with a grinding wheel(or disk grinder). However, if you can remove a small piece, it can be sent to a lab(for relatively little money) and a very complete analysis will be returned, there-by showing the way forward. If, indeed, it's cast iron, it will be best not to electrically weld it. On the other hand, if of wrought iron, it can be successfully electrically welded using an E6010 electrode with the SMAW "stick" process. Beleive this piece is most likely wrought iron, since as was mentioned earlier, cast iron was seldom used in these applications in tension. Respectfully, Dave Griner wasatch-rr-contractors.com |
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| Author: | David Johnston [ Sun Apr 20, 2008 2:03 am ] |
| Post subject: | Re: Welding cast iron for vertical tension rods ? |
At the Western Railway Museum we have also made similar repairs when changing side sills without disturbing the roof. The wrought iron rod was cut and threaded using a Ridgid 00R threader with the appropriate die. Then coupling nuts, which are available from McMaster Carr, were used to connect the two ends of the rods inside the wall. We have also made this splice where only a piece in the center of the rod was changed using right and left hand threaded coupling nuts. In one car there was a splice done by the railroad many years ago. The railroad had heated the end of the rod and bent it into a "U". They did the same with the new rod and just hooked them toghether inside the wall. We have also seen examples where the railroad had cut a thin slot in the top cord from the inside just below the roof just wide enogh to get a nut in. They then had worked the rod in and threaded it in the nut at the top and then nutted it at the bottom. I would be concerned with welding in that it is so hard not to set these very dry old cars on fire. |
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| Author: | Dennis Storzek [ Sun Apr 20, 2008 2:30 am ] |
| Post subject: | Re: Welding cast iron for vertical tension rods ? |
Matt Bumgarner wrote: Yes, it could be wrought iron, but the way it has corroded and laminated sure reminds me of some older artifacts that I have seen which are definitely cast iron. It is extremely brittle as well, but that could also be due to the corroded nature of the item.
Thanks for the input! Matt Laminated? You are looking at the signature feature of wrought iron. Cast iron is poured as a liquid, and cools to a homogenous crystalline mass. Wrought iron, on the other hand, was never completely melted; it was heated to a plastic state and hammered, the hammering consolidating the metal, and causing the non-metallic minerals combined in the ore to fracture and fall off. True wrought iron has a noticeable grain structure, which becomes even more evident as it rusts. There is a pretty good history of wrought iron production techniques here: http://en.wikipedia.org/wiki/Wrought_iron Unfortunately, no photos that show the grain structure. This info may also be useful: http://www.anvilfire.com/FAQs/wrought_iron.htm There is really no good repair; wrought iron was traditionally forge welded, that is two pieces were heated white heat and then hammered until they became one. If the bottoms of the rods are beyond reuse, I would suggest cutting them back to solid stock, and sistering pieces of mild steel rod alongside, making the connection with a couple of “Crosby” type cable clamps where they overlap. I assume once the car is complete, these will be hidden, and that the car is never going to actually be operated, so this should be sufficient to hold the frame together for static display. If the roof ever needs to be opened, then the top portion can be removed for display, and new mild steel rods installed at that time. |
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| Author: | Dave [ Sun Apr 20, 2008 7:06 am ] |
| Post subject: | Re: Welding cast iron for vertical tension rods ? |
Randy, wood is actually strongest in tension and weakest in shear and torsion. Not as strong as iron, however. dave |
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| Author: | Al Stangenberger [ Sun Apr 20, 2008 6:32 pm ] |
| Post subject: | Re: Welding cast iron for vertical tension rods ? |
Dave wrote: Randy, wood is actually strongest in tension and weakest in shear and torsion. Not as strong as iron, however.
dave More precisely, wood is quite strong in tension parallel to the grain. In fact, it is so strong in that direction that it is very hard to devise fasteners to take advantage of that strength -- the fasteners provide starting points for other types of failures like splitting. The ASTM test for wood tensile strength parallel to the grain uses a 2"x2" stick which can be held securely, and it is machined down to a cross-section of about 1/4" x 1/2" in the area where the failure will occur. Wood is quite weak in tension perpendicular to the grain. |
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| Author: | Dave [ Sun Apr 20, 2008 6:48 pm ] |
| Post subject: | Re: Welding cast iron for vertical tension rods ? |
Right you are Al, I should have been more specific. Leaves me to wonder though, what idiot would even contemplate putting wood in tension perpendicular to the grain? That's even intuitively obvious..... dave |
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